Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this disclosure and are not admitted to be prior art by inclusion in this section.
Available spectrum used by operators is limited and expensive. Radio link improvement is fast and is approaching its theoretical limit. The next leap of performance and capacity may come from network topology evolution by using a mix of macro cells and small cells, also referred to as Heterogeneous Network. Wireless Local Area Networks (WLANs), such as Wi-Fi (Wireless Fidelity) access, are also integrated into Heterogeneous Networks so as to improve user experience.
The business model for WLAN has changed from merely a home Internet gateway alternative to an essential part of the operator's bigger network data strategy. It would be advantageous for mobile operators to be able to offer packet based services to its customers over more networks such as WLAN than just its cellular networks.
Some operators are planning to deploy a system where LTE (Long Term Evolution) small cell and Wi-Fi AP (Access Point) is integrated. As shown in FIG. 1, the system includes a User Equipment (UE) 101, an integrated Base Station (BS) 102, a network Management System (NMS) or network management device 103, an Access controller (AC) 104 and a Wi-Fi AP 105. The integrated BS 102 provides LTE access and Wi-Fi access for UE 101. Wi-Fi AP 105 is a normal WLAN which is not integrated into LTE BS. The NMS 103 provides the management service both for the integrated BS 102 and the Wi-Fi AP 105. The AC 104 controls the Wi-Fi AP 105 in groups.
For a system where cellular network access and WLAN access are integrated into one BS, the inter-system radio interference may exist. For example, a TD-LTE small cell may use a frequency range of 2.3G-2.4 GHz for indoor coverage which is very close to a frequency band or range of 2.4G for Wi-Fi. Table 1 is a frequency list for Wi-Fi technology. Because of physically integration of some components, the adjacent frequency ranges may lead to serious radio interference in some scenarios.
TABLE 1Frequency List of IEEE 802.11 familyThroughputData RateModulationProtocolFrequency(Typical)(Max)Technique802.11a  5 GHz 0-25 Mbps 54 MbpsOFDM802.11b2.4 GHz   5 Mbps 11 MbpsDSSS -CCK802.11g2.4 GHz   23 Mbps 54 MbpsOFDM & DSSS802.11n2.4 GHz 5 GHz50-144 Mbps600 MbpsOFDM MIMO
One possible solution to reduce the inter-system radio interference of the co-existence scenario is to increase the antenna isolation of the difference systems which is usually required to be more than several meters isolation in vertical direction. However, the antenna isolation solution has some limit in performance improvement and it is not easy to be deployed for the integrated BS.
A US patent application US20130072209A1 discloses a wireless communication device including a first radio frequency (RF) transceiver (i.e. Bluetooth transceiver), a second RF transceiver (i.e. Wi-Fi transceiver) and a connection manager. The first RF transceiver is configured to transmit/receive RF signals in a first frequency band, and the second RF transceiver is configured to transmit/receive RF signals in a second frequency band that may be different from the first frequency band. The connection manager is coupled to the first and second RF transceivers and assists with channel selection by the first and second RF transceivers to reduce mutual interference between the first and second RF transceivers. The communication device here is a UE, just interference inside the UE is considered, and different UEs served by a same BS may have different channels or frequency bands, thus this solution can not solve the interference at the integrated BS side.
Another US patent application US20130016635A1 discloses a solution to mitigate potential interference between different radio access technologies (RATs) on a UE. According to this solution, traffic scheduling rules may be implemented so that communications of the individual RATs are timed in a manner that reduces interference. Another US patent application US20120327850A1 discloses a solution to reduce interference by controlling the timing of WLAN communications such that WLAN receptions do not overlap with transmissions of LTE. The two solutions are also for UE side, and can not efficiently solve the interference at the integrated BS side.